Hacket's father, Nev, told the media on Thursday that him and his mates were worried for Hackett's wellbeing.

"We're extremely worried about him," said Nev Hackett. "I would think that if anybody has seen him to contact media or the police or the Hackett family."

"Now's the time to be strong and do something positive and get a positive outcome.

"Grant, let us know where you are, we love you, and we want to help you."

Yesterday the 36-year-old was pictured handcuffed in the back of a police vehicle following what is alleged to be a domestic dispute with his parents. Hours later, Hackett had posted a photo on social media – his face bruised, his cheekbone swollen – alleging his brother had inflicted the damage.

Hackett's brother, Craig, pled to the media for his brother to seek help.

"This is not Grant Hackett," said Craig. "This is a completely different person; I don't know this person; my Mum and Dad don't know this person.

"He's there in body but not there in mind, and [a] soulless spirit."

In 2011, photos emerged of damage on Hackett’s multi-million dollar penthouse, believed to be by the swimmer in a fit of alcohol-fuelled rage. He has since divorced Candice Alley, as well as being dumped by Westpac as their brand ambassador, while a children’s charity distanced itself from him.

Any tweets I read about #granthackett that are negative I will unfollow.he is HUMAN & needs urgent psychological help ASAP #notcriticism 😒